diff --git a/setup b/setup
index 2e48fdaf3..22733893f 100755
--- a/setup
+++ b/setup
@@ -3710,6 +3710,33 @@ _hook_command_path() {
   return 1
 }
 
+# Hook syntax gate (#3032): Claude Code runs these shims through /bin/sh, and a
+# shell file that does not parse exits 2, which for a PreToolUse hook blocks the
+# tool call in every session on the machine. A half-edited or half-merged hook
+# must stop setup with its file and line before any registration is written or
+# healed, not install silently.
+_HOOK_SYNTAX_PROBLEMS=""
+for _hook in bin/gstack-session-update hosts/claude/hooks/question-log-hook \
+    hosts/claude/hooks/question-preference-hook hosts/claude/hooks/auq-error-fallback-hook \
+    hosts/claude/hooks/timeline-stop-hook autoplan/bin/phase-publication-hook; do
+  _hook_file="$CANONICAL_GSTACK_ROOT/$_hook"
+  [ -f "$_hook_file" ] || continue
+  if ! _hook_err=$(bash -n "$_hook_file" 2>&1); then
+    _HOOK_SYNTAX_PROBLEMS="${_HOOK_SYNTAX_PROBLEMS}
+  $_hook_err"
+  fi
+  if [ -f "$_hook_file.ts" ] && ! _hook_err=$(bun_cmd build --no-bundle --target=bun "$_hook_file.ts" 2>&1 >/dev/null); then
+    _HOOK_SYNTAX_PROBLEMS="${_HOOK_SYNTAX_PROBLEMS}
+  $_hook_file.ts:
+$(printf '%s\n' "$_hook_err" | sed 's/^/    /')"
+  fi
+done
+if [ -n "$_HOOK_SYNTAX_PROBLEMS" ]; then
+  echo "gstack setup: refusing to register hooks: a hook file does not parse, and Claude Code would block tool calls with it:$_HOOK_SYNTAX_PROBLEMS" >&2
+  echo "Fix: repair the file above (git -C \"$SOURCE_GSTACK_DIR\" status shows half-applied edits or merge conflicts), then re-run ./setup." >&2
+  exit 1
+fi
+
 # Heal-first: prune dead gstack hook entries and re-point survivors at the
 # stable install BEFORE any tag-presence guard below (a dead entry carrying the
 # tag otherwise blocks re-registration forever — the missing-Stop-hook failure
diff --git a/test/setup-hook-syntax-gate.test.ts b/test/setup-hook-syntax-gate.test.ts
new file mode 100644
index 000000000..fb47aa1ab
--- /dev/null
+++ b/test/setup-hook-syntax-gate.test.ts
@@ -0,0 +1,85 @@
+/**
+ * #3032: Claude Code runs gstack's hook shims through /bin/sh. A shim that
+ * does not parse exits 2, which for a PreToolUse hook blocks the tool call in
+ * every session. setup's gate parses every registered hook (bash -n on the
+ * shim, a Bun parse of its TypeScript entry) and stops with the file and line
+ * before any registration is written or healed.
+ *
+ * Runs the real gate block extracted from setup against a fixture install;
+ * driving all of ./setup here is disproportionate.
+ */
+import { describe, expect, test } from 'bun:test';
+import { spawnSync } from 'node:child_process';
+import * as fs from 'node:fs';
+import * as os from 'node:os';
+import * as path from 'node:path';
+
+const ROOT = path.resolve(import.meta.dir, '..');
+const SETUP = fs.readFileSync(path.join(ROOT, 'setup'), 'utf8');
+const START = SETUP.indexOf('# Hook syntax gate (#3032)');
+const END = SETUP.indexOf('# Heal-first: prune dead gstack hook entries');
+const GATE = SETUP.slice(START, END);
+const HOOKS = ['bin/gstack-session-update', 'hosts/claude/hooks/question-log-hook', 'hosts/claude/hooks/question-preference-hook',
+  'hosts/claude/hooks/auq-error-fallback-hook', 'hosts/claude/hooks/timeline-stop-hook', 'autoplan/bin/phase-publication-hook'];
+
+function fixture(): string {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'hook-syntax-gate-'));
+  for (const hook of HOOKS) {
+    fs.mkdirSync(path.dirname(path.join(root, hook)), { recursive: true });
+    fs.copyFileSync(path.join(ROOT, hook), path.join(root, hook));
+    if (fs.existsSync(path.join(ROOT, `${hook}.ts`))) fs.writeFileSync(path.join(root, `${hook}.ts`), 'export const ok = 1;\n');
+  }
+  return root;
+}
+
+function runGate(root: string) {
+  const script = `bun_cmd() { bun "$@"; }\nCANONICAL_GSTACK_ROOT='${root}'\nSOURCE_GSTACK_DIR='${root}'\n${GATE}\necho GATE_PASSED`;
+  const r = spawnSync('bash', ['-c', script], { encoding: 'utf8', timeout: 30_000 });
+  return { code: r.status, out: `${r.stdout}${r.stderr}` };
+}
+
+describe('#3032: setup refuses to register a hook that does not parse', () => {
+  test('the gate runs before any hook registration is healed or written', () => {
+    expect(START).toBeGreaterThan(-1);
+    expect(END).toBeGreaterThan(START);
+    const writes = [...SETUP.matchAll(/"\$SETTINGS_HOOK" (?:ensure-event|add-event|prune-stale|remove-source)/g)].map(m => m.index!);
+    expect(writes.length).toBeGreaterThan(0);
+    expect(Math.min(...writes)).toBeGreaterThan(END);
+  });
+
+  test('healthy hooks pass', () => {
+    const root = fixture();
+    try { expect(runGate(root)).toEqual({ code: 0, out: 'GATE_PASSED\n' }); }
+    finally { fs.rmSync(root, { recursive: true, force: true }); }
+  });
+
+  test('a half-merged shell shim stops setup with its file and line', () => {
+    const root = fixture();
+    try {
+      const shim = path.join(root, 'hosts/claude/hooks/question-preference-hook');
+      fs.appendFileSync(shim, '<<<<<<< HEAD\nif [ -n "$x" ]; then\n');
+      const r = runGate(root);
+      expect(r.code).toBe(1);
+      expect(r.out).toContain('refusing to register hooks');
+      expect(r.out).toContain(shim);
+      expect(r.out).not.toContain('GATE_PASSED');
+    } finally { fs.rmSync(root, { recursive: true, force: true }); }
+  });
+
+  test('a TypeScript entry with a syntax error stops setup with its file', () => {
+    const root = fixture();
+    try {
+      const ts = path.join(root, 'hosts/claude/hooks/timeline-stop-hook.ts');
+      fs.writeFileSync(ts, 'export const x = {;\n');
+      const r = runGate(root);
+      expect(r.code).toBe(1);
+      expect(r.out).toContain(`${ts}:`);
+      expect(r.out).toContain('Expected identifier');
+    } finally { fs.rmSync(root, { recursive: true, force: true }); }
+  });
+
+  test("every shipped hook in this checkout parses", () => {
+    const r = runGate(ROOT);
+    expect(r.out).toContain('GATE_PASSED');
+  });
+});